Production of insoluble sulfur



Patented Feb. 1, 1949 PRbDUCTION OF INS OLUBLE SULFUR Alvin Schallis,Jersey City, N. 'J., assignor to Stauffer Chemical Company, acorporation of California No Drawing. Application September 29, 1945.

Serial No. 619,418

v 7 Claims. (Cl. 23-224) This is a continuation in part of my applica- Vtion Serial Number 517,437, filed January '7, 1944, nowforfeited.

.This invention relates to the production ofinsoluble sulphur. Sulphursoluble in carbon disulphide is termed soluble sulphur, while that whichis not soluble is termed insoluble sulphur; to the latter material theterm "sulphur mu is frequently employed, and for convenience I mayemploy this term.

If one quenches molten sulphur in cold water, a mass of sulphur isproduced which, upon standing, solidfies and hardens. Upon being finelyground, it will be found that some portion of this material will beinsoluble in carbondisulphide. Endres, in Patent 1,875,372, states thatone-third of a sulphur so produced is insoluble in carbon disulphide,while the remainder is soluble. There is a steadily increasing demandfor insoluble sulphur and today it is generally produced by extractingthe soluble portion with carbon disulphide to leave as a remainder theinsoluble portion. This operation is obviously involvedand insolublesulphur is; therefore, expensive as compared to ordinary sulphur. If theinsoluble sulphur is permitted to standfor an extended period,particularly at a relatively ele-' vated temperature as can beencountered in warehouse storage, it will be found that a con-'siderable portion of the insoluble content has reverted to soluble form,thereby decreasing the value and usefulness of the material.

I have found that by treating insoluble sulphur with a small quantity ofa halogen the rate of reversion of the insoluble content to the solubleform is considerably decreased. This treatment of the insoluble sulphurwith halogen is effected subsequent to the formation of the insolublesulphur. This treatment may be accomplished in several ways. Thus (1)the halogen may be added directly to the insoluble sulphur in the drystate as by passing vapors of the halogen through or over the sulphur;or (2) a slurry of the solid insoluble sulphur in a solventfor thehalogen may be treated with the halogen (this may be followed by more orless complete extraction of the halogen and the soluble sulphur contentpresent); or (3) during the process of extracting the soluble sulphurfrom the insoluble sulphur, the last wash of solvent may contain thehalogen.

The sulphur employed as the source of insoluble sulphur can containthose organic compounds usually present as impurities in crude sulphurobtained from natural deposits in the United States. In fact, when theseare present in the insoluble sulphur, a halogen seems to be moreeffective, possibly because the halogenated organic compounds formedwith the impurities may be even more effective stabilizers than is thehalogen alone. Employment of a crude rather than an extremely highlyrefined sulphur as the source of insoluble sulphur is, therefore,possible.

Only a very small quantity of stabilizer need be added, such smallamounts that the effect can be termed catalytic, 1% and less only beingrequired. In any case, a trace of a halogen stabilizesthe sulphur. Thestabilizing effect is quite pronounced for the sulphur is stable evenwhen the halogen or halogen material is nearly all removed from thesulphur after the treatment. Reference to a halogen includes a halogenatom, the halogen'molecule, the halogen ion or a halide. The mechanismof the reaction is such that no'hypotheses can be made as to thepresence of intermediate activated complexes or ions, because no data isnow available to indicate the course of the reaction between the halogenor halide with S mu to form stabilized S mu. In any case we areconcerned only with the reactants and the final product and not with theintermediate complexes. The detailed mechaiiism of stabilization iscomplex; it may even differ as between stabilizing materials, yet thefinal result and final products are the same in that the product isstabilized. In any case, the halogen which has reacted with theinsoluble sulphur is not readily washed out and remains with theinsoluble sulphur; such a, small quantity is not readily determined byanalysis.

The following table indicates the stabilizing effect of various halogenswhen added to slurries of insoluble sulphur in carbon disulphide 01-lowed by washing with fresh carbon disulphide to remove the halogen. Thetest is conducted by subjecting a weighed quantity of the material to acarbon disulphide reflux stream in a Soxhlet extractor for four hours.This test provides con ditions conducive to an accelerated reversion. Inthe carrying on of this test, the sulphur should be in finely dividedform, to ensure that all soluble material is easily contacted forextraction, In determining the insoluble sulphur content and thereversion loss, a sample of the untreated sulphur to be tested is firstplaced Crootchcrucible and extracted with cold carbon disulphide 5. fora short time. The sulphur remaining is taken as being all insolublesulphur. A second sample is then extracted with carbon disulphide in aSoxhlet extractor for four hours. If the fraction of sulphur remainingin the Gootch crucible is taken as A and the fraction of sulphurremaining after the four-hour extraction as B," then the reversion losscan be expressed as follows:

Per cent reversion loss= g This approximates and gives an indication. ofthe loss which would be encountered in commercial handling of thematerial but under a much longer period of time.

Chlorine and bromine can be used as such but, these react readily withsulphur and. with any carbon disulphide present to form thecorresponding sulpho-halogen. For convenience, therefore, sulphurmonochloride, SzClz is used-,when it is desired to test theeffectiveness of only small quantities on a given mass of sulphur,rather than chlorine for the latter, being a. gas, is harder to handlethan the liquid sulphur chloride. The bromine probably was converted inpart to. SzBrz.

In another series of tests 60 gram quantities. of insoluble sulphur (75%insoluble-25% soluble) were treated with 100 c. c. quantities of carbonbisulphide containing the stabilizer to be tested.

The carbon bisulphide was then allowed to evaporate into the atmosphereso the stabilizer re mained. Each dry sample was then sifted andanalyzed,- The following table gives the, results, upon treatment withthe indicated stabilizer:

It will be noted that the untreated sample reverted at. the rate of 11%a month under conditions comparable to summer warehouse storage whilethe treated material reverted at only 2% In another series of tests, 80gram samples of an insoluble sulphur (75% insoluble-25% soluble) weretreated at room temperature (-15-20 C.)

for at least 24 hours with c. c. quantities of carbon bisulphidecontaining the indicated weight of stabilizer. The slurry was filteredand washed in each case with 500 c. c. of fresh carbon bistable product.

sulphide, care being taken to press each filter cake and avoid cracksthrough which the bisulphide could short circuit. The washed cake wasthen spread out and allowed to air dry; it was then sifted through ascreen to produce a uniform product.

" Table 111 Monthly reversion rate,

per cent loss at 90 F.

Stabilizer Itwill be observed upon comparing the results of Tables I andIII with those in Table II that sulphur from which the soluble sulphurand stabilizer have. been" extracted is. generally more stable than thatin which the stabilizer is. present. The stabilizing treatment ispreferably effected; therefore, on. the crude insoluble sulphur andlater the stabilizer and soluble sulphur are extracted. This ensures thehighestgrade and most In. place of using the, halogen as such one canemploy any compound containing a halogen in such a. linkage that, whenvadded to the sulphur, the compound is a halogen donor to an. extentsufficient to effect. the; stabilization through a mechanism.in-volvingprobable halogen liberation. Thus one can use inorganiccompounds such as titanium tetrachloride, SOClz, phosphorousoxychloride, phosphorus tri-chloride, phosphorous. pentachloride,silicon tetrachloride. One can also use: organic; compounds whichliberate at leasta small quantity of halogen in contact with the sulphursuch as allylbromide, allyl chloride. All useful compounds are, ineifect, halogen donors and are, therefore, merelyanother halo gensource. On this-basis, (1) thereagent should contain a halogen-which cancombine with thev sulphuuandi (2.) the reagent shouldfnot contain norform a residue detrimental to the stability (as iron or an. ironsulphide'as in the caseof' added ferric chloride; these are knowntoaccele rate reversion To facilitate treatment of the sulphur, it: isdesirable that the reagent have either an appreciable vapor pressure orelse be sufiiciently soluble in the solvent used to extract solublesulphur that itcan be added and substantially removed with this solvent.

I claim: i i

1., A process for reducing the rate of reversion of that, form ofsulphur which is insoluble in carbon disulphide to that.v form which issoluble incarbondisulphide comprising incorporating, in preformedsulphur containing at least a third by weight of'said insoluble sulphur,less than about 1%. of a halogen on the weight of the sulphur.

A process for reducing the rate of reversion of that form of sulphurwhich is insoluble in carbon disulphide to that form which is soluble incarbon disulphide comprisin washing sulphur containing at least a thirdby weight of said insoluble sulphur with a solvent for the carbondisulphide solublesulphur, the solvent. containing a halogen in anamount less than about. 1% of the weight ofthe. sulphur.

3. A process for reducing the rate of reversion of that form of sulphurwhich is insoluble in carbon disulphide to that form which is soluble incontaining at least a third by weight of insoluble sulphur with a fluidcontaining a halogen in an amount less than about 1% of the weight ofthe sulphur to stabilize the insoluble sulphur.

4. A process for reducing the rate of reversion of that form of sulphurwhich is insoluble in car bon disulphide to that form which is solublein carbon disulphide comprising incorporating, in a preformed sulphurcontaining at least a third by weight of said insoluble sulphur, lessthan about 1% of a halogen on the weight of the sulphur; and extractingthe sulphur with a solvent for (a) the sulphur present which is solublein carbon disulphide and (b) the halogen to remove substantially all ofthe soluble sulphur present and the added halogen. v

5. A process for reducing the rate of reversion of that form of sulphurwhich is insoluble in carbon disulphide to that form which is soluble incarbon disulphide comprising treating sulphur containing at least athird by weight of said insoluble sulphur with a fluid containing lessthan about 1% of a halogen on the weight of insoluble sulphur treated tostabilize said insoluble sulphur against reversion to the soluble form,and thereafter extracting the sulphur with a solvent for (a) the sulphurpresent which is soluble in car.- bon disulphide and (b) the halogen toremove substantially all of the carbon disulphide soluble sulphurpresent and the added halogen.

6. A process for reducing the rate of reversion of insoluble to solublesulphur in sulphur which has been chilled from a high temperature andextracted with a solvent to remove the soluble form and which containsat least a third by weight of insoluble sulphur, the process comprisingincorporating a halogen in an amount less than about 1% in said sulphur.

'7. A process for reducing the rate of reversion of insoluble to solublesulphur in preformed sulphur containing at least a third by weight ofthe insoluble sulphur, which comprises incorporating a halogen in anamount less than about 1% of the weight of the sulphur, and extractingfrom the sulphur with a solvent substantially all of the added halogenand the soluble sulphur present.

ALVIN SCHALLIS,

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date Ceccon Nov. 17, 1936 OTHER REFERENCESNumber

